The present invention generally relates to an electric generator and specifically, to a method and a system for detecting collector flashover.
Generators are an indispensible part of power systems and are extensively used for power generation. Generators work on the principle of electromagnetic induction. A rotating magnetic field is generated either by a set of permanent magnets or electromagnets. Magnetic flux of the rotating magnetic field is linked to stationary coils. Due to rotation of the magnetic field, the flux linked to stationary coils varies in a sinusoidal fashion, causing a sinusoidal variation of voltage across the terminals of the stationary coils.
Typically, the stator of a generator is provided with slots for winding the stationary coils. The rotor is provided with magnets for generating a rotating magnetic field. The magnets disposed in the rotor may be permanent magnets or electromagnets. In most generators electromagnets are provided. To magnetize the electromagnets a current is applied on rotor coils wound over the said electromagnets. For continuous flow of current in the rotor coils one or more collector rings and brush arrangements are used. Under normal operation, the brushes maintain an optimum pressure on the collector rings so that the circuit is always closed.
In due course of time, the pressure of the brushes on the collector rings is reduced. Also, the collector rings and the brushes undergo continuous wear and tear that sometimes results in gaps between the collector ring and the brush. Arcing may take place in the gap, which may further lead to a flashover, hereinafter referred to as collector flashover. This may lead to tripping of the generator, thereby causing a forced outage.
According to currently existing techniques, periodic inspections of the generator are carried out for preventing collector flashovers. When damage to the collector rings or the brushes is detected, corrective action is taken to prevent collector flashovers. However, inspecting the generators frequently is inconvenient. Also, for every inspection, the generator needs to be shut down. The existing methods cannot predict a potential collector flashover while the generator is in operation.
Thus, there is a need for a system and method for a more efficient detection of collector flashovers.